Spark plug pin gapping tool

ABSTRACT

A spark plug gapping tool is disclosed for adjusting the spark gap width of a pin type plug. A plate is threaded to position the spark plug shell with the end of the shell extending beyond the surface of the plate. A pusher pin member is provided to move against the firing end of the ground electrode pin to widen the spark gap, or the working end of an adjusting screw can be used to narrow the gap.

United States Patent 1 Paxton Dec. 11, 1973 SPARK PLUG PIN GAPPING TOOL1,990,430 2/1935 Fitzgerald 33/168 R 2,193,886 3/1940 Schutz [75] [mamm-Pam, 2,432,703 9/1949 Call 12/125 [73] Assignee: General MotorsCorporation,

Detroit, Mich. Primary Examiner-Richard J. Herbst AssistantExaminer-Gene P. Crosby [22] Flled 1972 Attorney-Sidney Carter et al.[2]] Appl. No.: 238,132

, [57] ABSTRACT [52] US. Cl. 72/293, 29/203 R, 72/454, A spark pluggapping tool is disclosed for adjusting the 72/457 spark gap width of apin type plug. A plate is threaded [51] Int. Cl B2111 26/02 t p siti nth spar plug sh ll with th end of th [58] Field of Search 72/293, 454,457, shell extending beyond the surface of the plate. A 72/125; 29/203R, 25.12 pusher pin member is provided to move against the firing end ofthe ground electrode pin to widen the [56] References Cited spark gap,or the working end of an adjusting screw UNITED STATES PATENTS can beused to narrow the gap. 1,985,410 12/1934 Isaacs 72/293 I 4 Claims, 3Drawing Figures SPARK PLUG PIN GAPPING TOOL It haslong been recognizedthat the spark plug firing gap requires periodic adjustment in ordertomaintain maximum efficiency of an ignition system in an internalcombustion engine. This results from the fact that the firing end of theplug operates under severe conditions of thermal stress-and in anenvironment conducive to the erosion and corrosion of the electrodeelements.

Typical of the gapping tools available in the prior art are devicesdisclosed by the patents to C. A. Schulz, U.S. Pat. No.2,193,886datedMar. 19, 1940 and entitled Spark Plug Tool, M. D.Fitzgerald, U.S. Pat. No. 1,990,430 dated Feb. 5, 1935 and entitledGauging Tool for Spark Plugs, and the patent to E. A. Call, U.S. Pat.No. 2,482,703 dated Sept. 20, 1949 and entitled Aviation Spark PlugAdjusting Tool. Each of these patents discloses mechanisms for adjustingthe gapsof the standard type plug having the gap forming portions of theelectrodes extending beyond the end of the spark plug shell.

The pin type or retracted gap spark plug is not suited for use with suchtools since the electrode elements are recessed within the spark plugshell. A gapping tool currently available for use with such retractedgap plugs comprises a plate-like member having a heartshaped openingtherein forming a V-shaped saddle on which the firing end of the plugispositioned with the ground electrode pin hole facing an adjusting screwthreaded into the plate. Turning the adjusting screw into the openingand into contact with the ground electrode pin forces the pin closer tothe center electrode. In order to widen the retracted gap a pin isprovided on the outer surface of the block adapted to fit within the gapbetween the ground and center electrodes. A second adjusting screw isprovided with a V-block positioned on the end thereof adapted to seatthe threaded end of the plug in order to push the plug with respect tothe pin on the outer surface of the block and thus move the groundelectrode pin away from the center electrode. It is readily apparentthat the force applied by the pair of adjusting screws can deform thethreads on the spark plug shell with resultant damage to the threadedopenings in the engine block.

It is therefore an object of my invention to provide a gapping tool foruse with retracted gap type plugs whereby the gapping forces applied bythe tool cannot damage the threaded portion of the spark plug shell. Itis another object of my invention to provide a spark plug gapping toolfor use with spark plugs of different shell diameters.

These and other objects of my invention are accomplished by providing aplate having threaded means for threadedly positioning the spark plugshell with its end extending beyond the surface of said plate, a shaftpositioned in said plate, the longitudinal axis of said shaft beingparallel to the axis of said threaded means, an adjusting screwthreadedly positioned in said shaft, the axis of said adjusting screwbeing perpendicular to the axis of said threaded means, link meansrotatably positioned on said shaft adjacent said adjusting screw theplane of rotation being perpendicular to the axis of said threadedmeans, a pusher pin positioned on one end of said link means andextending toward said threaded means and being adapted to be positionedin the spark plug gap, said link means being adapted to be contacted bythe working end of said adjusting screw to move the pusher pin againstthe firing end of the ground electrode pin to widen the spark gap, saidworking end being adapted to contact the outer end of the groundelectrode pin topush the electrode closer to the ground electrode tonarrow the gap.

The device of my invention is readily understood from the followingdescription taken in conjunction with the drawing in which:

FIG. 1 is a plan view of a preferred embodiment of the gapping toolshowing the firing end of a spark plug threaded into the tool forgapnarrowing;

FIG. 2 isa side view taken on line 2-2 of FIG. I with the spark plugremoved and with the shell receiving bores not shown for the sake ofclarity; and

FIG. 3 is an isometric view of the gapping tool showing the spark plugfiring end positioned for gap widening.

The gapping tool of I my invention, as shownin the drawing, comprises aplate 1 provided with threaded means 2 for receiving and retaining infixed position the threaded end 20 of the spark plug shell. lnthepreferred embodiment, as shown in the drawing, the retaining meansconsists of a threaded bore sized to receive the threaded firing end ofthe spark plug. Also as shown, two or more threaded bores may be used inorder to accommodate the various sizes of spark plugs.

A shaft 3 is positioned within the plate 1 with its longitudinal axisparallel to the axis of the threaded bores 2. Snap rings 4 are providedon each end of the shaft 3 in order to retain the shaft within theplate 1. The shaft 3 is rotatable and slidable with respect to the platein order to enable easy positioning of the gap adjusting mechanism ofthe tool regardless of where the spark plug firing end 20 is positionedin the plate. A threaded adjusting screw 5 is positioned in the shaftfor threaded adjustment with respect thereto, the axis of the adjustingscrew being perpendicular to the axis of the threaded bores 2. As isclearly shown in FIG. 1, the working end 6 of the adjusting screw isformed so as to fit within the bore 21 formed in the threaded wall 20 ofthe spark plug shell and to abut the outer end 22 of the groundelectrode pin press fitted within the bore.

As is clearly shown in FIGS. 1 and 3, the tool of my invention isprovided with link means 7 for enabling gap widening adjustment of thepin ground electrode. More particularly, a link 8 is rotatably mountedat one end on shaft 3, a pusher arm 9 being rotatably mounted at one ofits ends on the other end of the link. As shown in the drawing, link 8and arm 9 are joined by means of the rivet or pin 10. The link 8 and thepusher arm 9 are free to rotate about their mounting points in planesparallel to each other. A pusher pin II is positioned on the free end ofthe pusher arm 9 and extends axially toward the plate and its threadedbores 2, the pusher pin being adapted to be positioned in the spark pluggap.

As is readily seen in FIGS. 2 and 3, the pusher pin 11 is axiallyadjustable in the pusher arm 9 in order that the extending length of thepusher pin may be adjusted so as to fit between the two electrodes inthe gap. As shown, pin 11 is threaded in arm 9, it being obvious thatother means, i.e., set screw positioning, may be used. As is also clearin FIGS. 2v and 3, the end of the pusher pin 11 which fits in the sparkgap has a centerbore to enable the end to fit over the center electrodewith one portion of the annular side wall in the gap between theelectrodes. The portion of the annular side wall opposite that portionpositioned in the gap is removed to form an aperture 12 to permit thepusher pin 11 to be moved over the end of the center electrode 23 andapply the necessary force against the firing end 24 of the groundelectrode to thus widen the gap.

In operation, as shown in FIG. 1, the firing end of the spark plug isthreaded into the appropriate threaded bore 2 to locate the groundelectrode shell bore 21 in axial alignment with the adjusting screw 5.Since the shaft 3 is both free to rotate and slide with respect to thethreaded bore, this alignment is readily accomplished. The spark pluggap is narrowed by moving the working end 6 of the adjusting screw intoabutment with the outer end 22 of the ground electrode pin and forcingthe pin closer to the center electrode 23. Widening of the gap is simplyaccomplished by aligning the pusher pin over the end of the spark plugshell so that movement of the link means 7 toward the plate 1 positionsthe pusher pin 11 in the spark plug gap. As is readily apparent, thefreedom of the link 8 and the pusher arm 9 to rotate with respect toeach other and with respect to the plate 1, as well as the axial freedomof movement of the shaft 3 permit the ready alignment of the pusher pin11 with the spark gap. On threading the adjusting screw into the shaft3, the working end 6 is placed in abutment with the pusher arm 9 andfurther forward movement pushes the ground electrode pin away from thecenter electrode. As can be seen in FIG. 3, a notch 14 may be providedon the side of the pusher arm to prevent slippage of the working end 6on the surface of the arm.

Modifications of my invention will be readily apparent to those skilledin the art and it is intended that such modifications be within thescope of my invention. For example, it would be obvious that in lieu ofusing a plurality of threaded bores, a plurality of threaded bushings ofdifferent bore diameter may be removably positioned in the plate toenable use of the tool with different size plugs. Accordingly, the scopeof my invention is as defined in the claims which follow.

What is claimed is:

l. A spark plug gapping tool for adjusting the spark gap width of aretracted gap type plug characterized by a ground electrode pinpress-fitted in the threaded portion of the spark plug shell adjacentthe end thereof and extending into spaced relationship with the centerelectrode to define a spark gap, said tool comprising a plate havingthreaded means for threadedly positioning the spark plug shell with itsend extending beyond the surface of said plate, a shaft positioned insaid plate, the longitudinal axis of said shaft being parallel to theaxis of said threaded means,'an adjusting screw threadedly positioned insaid shaft, the axis of said adjusting screw being perpendicular to theaxis of said threaded means, link means rotatably positioned on saidshaft adjacent said adjusting screw, the plane of rotation beingperpendicular to the axis of said threaded means, a pusher pinpositioned on the free end of a pusher arm attached to said link meansand extending toward said threaded means and being adapted to bepositioned in the spark plug gap, said pusher arm being adapted to becontacted by the working end of said adjusting screw to enable force tobe applied upon advancement of said screw to move the pusher pin againstthe firing end of the ground electrode pin to widen the spark gap, saidworking end being adapted to contact the outer end of the groundelectrode pin to push the electrode closer to the center electrode tonarrow the gap.

2. A gapping tool in accordance with claim I wherein said link meanscomprises a link mounted at one end on said shaft, said pusher armrotatably secured at one end to the other end of said link with theplanes of rotation of said link and said pusher arm being parallel, saidpusher pin being positioned in said pusher arm.

3. A gapping tool in accordance with claim 2 wherein said shaft isrotatable and slidable with respect to said plate, said threaded meansbeing at least two spacedapart threaded bores adapted to receive sparkplug shells of different diameters.

4. A gapping tool in accordance with claim 3 wherein said pusher pin isaxially adjustable in said pusher arm to enable positioning in the sparkgap regardless of the retracted positioning of the spark gap within theshell, and wherein a notch is provided in the side of said pusher armadjacent said pusher pin to retain the working end of said adjustingscrew on said pusher arm during gap adjustment.

1. A spark plug gapping tool for adjusting the spark gap width of aretracted gap type plug characterized by a ground electrode pinpress-fitted in the threaded portion of the spark plug shell adjacentthe end thereof and extending into spaced relationship with the centerelectrode to define a spark gap, said tool comprising a plate havingthreaded means for threadedly positioning the spark plug shell with itsend extending beyond the surface of said plate, a shaft positioned insaid plate, the longitudinal axis of said shaft being parallel to theaxis of said threaded means, an adjusting screw threadedly positioned insaid shaft, the axis of said adjusting screw being perpendicular to theaxis of said threaded means, link means rotatably positioned on saidshaft adjacent said adjusting screw, the plane of rotation beingperpendicular to the axis of said threaded means, a pusher pinpositioned on the free end of a pusher arm attached to said link meansand extending toward said threaded means and being adapted to bepositioned in the spark plug gap, said pusher arm being adapted to becontacted by the working end of said adjusting screw to enable force tobe applied upon advancement of said screw to move the pusher pin againstthe firing end of the ground electrode pin to widen the spark gap, saidworking end being adapted to contact the outer end of the groundelectrode pin to push the electrode closer to the center electrode tonarrow the gap.
 2. A gapping tool in accordance with claim 1 whereinsaid link means comprises a link mounted at one end on said shaft, saidpusher arm rotatably secured at one end to the other end of said linkwith the planes of rotation of said link and said pusher arm beingparallel, said pusher pin being positioned in said pusher arm.
 3. Agapping tool in accordance with claim 2 wherein said shaft is rotAtableand slidable with respect to said plate, said threaded means being atleast two spaced-apart threaded bores adapted to receive spark plugshells of different diameters.
 4. A gapping tool in accordance withclaim 3 wherein said pusher pin is axially adjustable in said pusher armto enable positioning in the spark gap regardless of the retractedpositioning of the spark gap within the shell, and wherein a notch isprovided in the side of said pusher arm adjacent said pusher pin toretain the working end of said adjusting screw on said pusher arm duringgap adjustment.